I bought my phone in January, and the last couple months it hasn't been working. Every time I turn it on, it displays the message 'Invalid SIM' and tells me I can only make emergency calls. My sister, wh*also has a TracFone, had a similar problem, but in her case simply turning the phone off and on again would fix it. That doesn't work with mine. We took the SIM card out and it looks just fine, my phone is active, still has service coverage, and it is the original card that came with the phone. What do I need to do to fix this?